<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>作用域</title>
</head>
<body>
    <script>
        alert(d);
        var a = 10;
        var b = "hello";
        c = true;
        function fun (){
            alert("hello");

        }

        var d = 35;
    </script>
</body>
</html>